Rice in soup

I'm a little bit at a loss here. I'm making soup again for my mom because she's sick. I made chicken noodle the other night and my dad asked me to use rice this time because he likes rice better. I said sure

But now I don't know how much rice to use. The soup pot is very big. I use about 4lbs of chicken and at least one whole bag of egg noodles.

Help me. Lol I don't want to just wing it and accidentally put too much rice in.